1. Field of Invention
The present invention relates to the field of computer networks. More specifically, the invention relates to a computer processor that has been designed with specific features for network processing.
2. Description of Related Art
To ensure the integrity of data, most communication protocols implement a checksum. To use a checksum, a sending unit calculates a first checksum based upon a data packet that will be transmitted. The sender then transmits the data packet along with the accompanying checksum to a receiving unit. The receiving unit calculates a second checksum for the received data packet. The receiver then compares the second checksum with the first checksum sent by the sending unit. If the two checksum values match, then the data packet was transmitted without error. However, when an error occurs, the two checksum values will not match and the receiving unit will reject the data packet.
Several internet protocols (e.g. UDP and TCP) use checksums to check for data corruption in data headers and/or packet bodies. The standard internet checksums use one's complement arithmetic. Several references such as Braden, R., Borman, D., and Partridge, C., "Computing the Internet Checksum," Network Working Group RFC-1071, ISI, Cray Research, and BBN Labs, September 1988; Mallory, T., and Kullberg, A., "Incremental Updating of the Internet Checksum," Network Working Group RFC-1141, BBN Comm., Jan. 1990; Plummer, W., "TCP Checksum Function Design," IEN-45, BBN, 1978, included as an appendix in RFC-1071; and Rijsinghani, A., "Computation of the Internet Checksum via Incremental Update," Network Working Group RFC-1624, Digital Equipment Corp., May 1994 teach software methods of calculating the internet checksum.
The Internet has been expanding at exponential rates. The increasing loads upon the global internet infrastructure has created a demand for very fast internet switching devices. To meet this demand, specialized hardware implementations of network processing devices have been introduced. For example, a hardware implementation of a device to calculate internet checksums is disclosed in Touch, J., and Parham, B., "Implementing the Internet Checksum in Hardware," Network Working Group RFC-1936, ISI, April 1996. Thus, there is a strong demand for high speed hardware for performing network processing.